This invention generally relates to intravascular catheters, particularly catheters for use in percutaneous transluminal coronary angioplasty (PCTA) or for the delivery of stents.
In a typical PTCA procedure a dilatation balloon catheter is advanced over a guidewire to a desired location within the patient""s coronary anatomy where the balloon of the dilatation catheter is properly positioned within the stenosis to be dilated. The balloon is then inflated with radiopaque liquid at relatively high pressures (generally 4-12 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations may be needed to effectively dilate the stenosis. The catheter may then be withdrawn from the stenosis or advanced further into the patient""s coronary anatomy to dilate additional stenoses.
In addition to the dilation of stenoses, balloon catheters similar to those described above are used to deploy stents within a patient""s body lumen after a dilatation has been completed or simultaneously with the dilatation in order to maintain lumen patency. In this case an expandable stent is disposed about the exterior of the balloon on the distal extremity of the catheter and the catheter is then advanced within the patient""s body lumen until the stent mounted on the exterior of the balloon is at the location in which the stent is to be deployed, e.g. usually at the stenotic site of a previous dilatation. The balloon is inflated so as to expand the stent against the wall defining the body lumen and then the balloon is deflated and the catheter withdrawn from the patient""s body lumen.
Advances in the development of balloon catheters for both dilatation and stent deployment have made the selection of materials difficult because of conflicting requirements. For example, higher dilation pressures has made the sealed bonding of the balloon the catheter shaft a greater requirement, but the materials from which the high pressure balloons are made, e.g. polyethylene terephthalate, polyamide (e.g. nylon) and the like, have limited the materials to which the balloon can be bonded, and thus, the materials from which the catheter shaft can be made, particularly the distal extremity of the catheter shaft where the balloon is located.
If the distal tip of an in travascular catheter is to have non-traumatic characteristics to minimize damage when passing through a body lumen, additional material limitations come into play because typical non-traumatic tips are formed from short tubular members made of relatively soft polymeric material which are secured by adhesive or fusion bonding to the distal tip of the tubular distal extremity of the catheter.
Other complicating factors in the selection of materials for intraluminal catheters is the usual requirement that the proximal shaft be much longer and much less flexible than the distal shaft section so that the proximal shaft section provides the push to the catheter and so that the more flexible distal shaft section can be readily advanced through tortuous anatomy.
The difficulties in material selection and the more complicated construction of the more recently developed catheters make their manufacture more difficult and more expensive. What has been needed is a catheter structure which simplifies the material selection and reduces the cost of manufacture. The present invention satisfies these and other needs.
This invention is directed to an improved multilayer member for an intraluminal catheter which can be readily bonded to other catheter parts.
The multilayer member of the invention has a first layer which is fusion bondable to another catheter component and an adjacent second layer which has greater lubricity than the first layer. The first layer preferably has a melting point which is lower than the melting point of the adjacent second layer so that when the first layer is fusion bonded to another catheter component, the adjacent layer of the multilayer member is not deformed or otherwise misshapen by the heat from a bonding procedure. In a presently preferred embodiment of the invention, the multilayered member is in a tubular form with the second layer on the inside of the tubular member defining an inner lumen extending through the tubular member. The first layer which has a melting point lower than that of the second layer forms at least in part the outer layer of the tubular member.
In one aspect of the invention, the catheter has an elongated shaft with a proximal end, a distal end, a port in the distal end and a guidewire lumen extending through at least the distal portion of the catheter to and in fluid communication with the port in the distal end of the catheter shaft. In accordance with this aspect, the elongated shaft of the catheter has a multilayer tubular member with a first or outer layer which is fusion bondable to another catheter component and a second or inner layer which has lubricious properties. A high strength outer layer may be bonded to at least part of the first layer to provide additional strength and pushability. The first layer should have a melting point which is at least 20xc2x0 C., preferably at least 30xc2x0 C. lower than the melting point of an adjacent polymeric layer, so that the adjacent layer is not distorted by the heat from the fusion bonding procedure.
The material from which the first layer of the multilayered member, which has a lower melting point than the adjacent second layer, is selected so as to be. compatible with the polymeric material of the catheter component to which it is to be secured. A presently preferred lower melting point polymeric material is a polyolefin based copolymer with not more than 35% (by weight) reactive monomer forming the copolymer. A suitable polyolefin material is copolymerized with one or more monomers selected from the group consisting of carboxylic acid or acrylic acid or anhydride thereof and preferably is unsaturated. A presently preferred polyolefinic material is a polyethylene based adhesive polymer such as ethylene-acrylic acid copolymer which is sold commercially as PRIMACOR by Dow Chemical Co. or as ESCOR by EXXON or as PLEXAR by Quantum Chemical Corp. Other suitable materials include polymers which have been modified by reactive extrusion having a durometer range of about Shore A 80 to about Shore D 80, preferably about Shore A 90 to about Shore D 70.
The second or inkier layer of the multilayer member having lubricious properties should have a coefficient of friction (both static and dynaric) of less than 0.35 and preferably less than 0.30. Suitable polymeric materials having the aforesaid coefficient of friction include polyethylene, polytetrafluoroethylene and other fluoropolymers.
As previously mentioned a third layer may be provided on the side of the first layer opposite side in contact with the second layer and may be formed of various polymeric materials to provide a catheter shaft with additional push and to prevent collapse or kinking of the tubular member in manufacturing or use. Suitable polymeric materials for the third layer include high density polyethylene, polyethylene terephthalate (PET), polyamide, a thermoplastic polyurethane, polyetheretherketone (PEEK) and the like.
All or most of the layers of the multilayered tubular member are preferably selected or modified so that they can be melt processed, e.g. coextruded, simultaneously or sequentially, and as a result the polymeric materials of the various layers should be compatible in this regard or made compatible by appropriate additives to the polymers.
In one presently preferred embodiment of the invention, the catheter is a dilatation catheter for angioplasty or stent delivery having a balloon on a distal shaft section with a multilayered inner tubular member which extends through and distal to the balloon and which defines at least in part a guidewire lumen extending to and in fluid communication with a port in the distal end of the catheter. In this instance, the multilayered inner tubular member has a bondable outer layer and the polymeric material thereof is selected to facilitate the fusion bonding of the distal skirt of the balloon to the outer layer of the inner tubular member. The multilayered inner tubular member also has an inner layer having lubricious properties which defines at least part of the guidewire lumen.
Another embodiment of the invention is directed to an intraluminal catheter wherein the multilayered tubular member forms at least part of the shaft of the intraluminal catheter and the low melting point material of the outer bonding layer of the multilayered tubular member extends beyond an adjacent layer to form a non-traumatic distal tip on the catheter shaft.
In yet another aspect of the invention, the catheter is provided with a nontraumatic distal tip which is fusion bonded to at least the bondable layer on the multilayered tubular member. While a fusion bond somewhat limits the selection of material for the bondable layer, the preferred material discussed above, namely the polyethylene based adhesive such as PRIMACOR, ENCOR or PLEXAR facilitates fusion bonding to a wide variety of materials including polyethylene, PET, polyamide, polyurethane, PVC and copolymers such as PEBAX(copyright) and HYTREL(copyright) and the like.
In most instances the wall thickness of the fusion bondable layer of the multilayered tubular member should be less than half the wall thickness of the tubular member, preferably less than 40% of the total thickness of the member. The inner and outer dimensions of the tubular member generally follow the dimensions of other tubular members from which intravascular catheters are made.
The present invention provides an improved multilayered member which greatly facilitates bonding of one catheter component to another catheter component, particularly bonding the skirt of dilatation balloon to the inner tubular member of the catheter.
These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings.